There is one thing (or more--G!) that I have never understood about all these calculations on Reynolds numbers, etc. They keep comparing gases (air) and liquids (water) as if they behave in the same way. Gases, such as air, are very compressible. Liquids, such as water, are for all practical purposes, totally incompressible. So why are they being treated as behaving in the same way? Please enlighten me.
Puff